Various remote control systems are now in use. In one system such as a smart entry system, a portable device (electronic key) carried by a vehicle user transmits a response signal in return to an interrogatory signal periodically transmitted from a vehicle. This response signal includes identification information therein. If the portable device is validated based on the identification information, vehicle doors are unlocked and a vehicle engine starting is enabled. This system is, however, disadvantageous in that the doors may be unlocked and the engine may be started even if the portable device is used by an unauthorized vehicle user.
JP 2000-352245A proposes another system, which validates a vehicle user based on biometric information such as a finger print, a voice print or a face picture of the vehicle user in addition to identification information of a portable device. This system thus restricts vehicle door unlocking and engine starting by an unauthorized user.
In this system using biometric information, a CCD sensor may be used to optically detect the finger print, the face picture or the like. It is necessary to expose a light inlet opening of the CCD sensor. The surface of a glass in the light inlet opening is subjected to dust or the like. The surface of the glass will be stained or blurred, particularly when the finger or a part of a user body is required to touch the glass for biometric detection. This causes poor detection of the biometric information of the user.